If you stand in Benjamin Marks' living room, you can hear the high-pitched hum. It's distant but not too far off, as though a next-door neighbor were running a vacuum cleaner or a blender.

Actually, the sound comes from a much larger appliance -- the new outdoor incinerator of Baltimore County General Hospital.

The $750,000 unit, which began operation in January, stands a few hundred yards from Mr. Marks' home in the west county community of Stevenswood.

Even when his doors and windows are closed, the noise is audible in the house from morning to night, said Mr. Marks, 24, a salesman for a local printing firm.

What burns Mr. Marks up isn't so much the volume of the noise as its all-day consistency. "It's a lovely sound to wake up to," he said sarcastically.

Noise pollution isn't the only problem Stevenswood residents have blamed on the medical-waste incinerator.

Powdered lime, used to neutralize acid gases in the incinerator, has spilled from the unit and gotten into nearby storm drains.

In March and earlier this month, Mr. Marks observed thick white streaks of lime in the stream that runs behind his family's house.

He recorded the damage with color photographs and videotape, and also took photos and tape of the incinerator at the time of the lime leaks.

One photo shows dried lime dropping from a discharge chute into a plastic trash can. About 1 foot of space separates the end of the chute from the can.

In the photo, the exterior of the can and much of the ground around it are blanched from the lime.

State and county environmental officials made a quick investigation and traced the lime in the stream to the incinerator.

Hit with violation notices, the hospital flushed the stream and pledged to prevent a recurrence.

County General spokesman Lee Kennedy said the hospital plans to install a covered chute to carry lime from inside the incinerator to a covered container.

Mr. Kennedy acknowledged that the hospital had been guilty of "faulty housekeeping.

"We're sorry it happened, but we've been forthcoming with the state, the county and the community about fixing the situation," he said.

The 750-member community remains wary, however. Residents remember the hospital's previous incinerator as a source of woe.

On different occasions, the hospital overloaded waste, allowed excessive pollutants into the air and failed to report a mechanical malfunction, said Michael Kendall, a supervisor with the county's Department of Environmental Protection and Resource Management.

Community feeling toward the privately owned hospital and its incinerator was summed up by George Murphy, president of the Liberty Road Community Council, an umbrella organization of 30 local neighborhood associations.

"We value the hospital, but we don't value their incinerator," Mr. Murphy said.

Like other Maryland hospitals, Baltimore County General built a new incinerator in response to recently enacted state laws aimed at cleaning up medical-waste emissions. The new units burn cleaner, but their emission control devices make more noise.

Mr. Marks, a vice president of the Stevenswood Improvement Association, and Ella White Campbell, the association's president, say they and other residents have heard the incinerator running as late as 11:30 p.m. They say that's three hours past the shutdown time promised by hospital officials.

Mr. Kennedy said such late-night operation is rare.

"We don't usually go beyond 8 p.m.," he said. "Possibly the neighbors are hearing air conditioners or boilers located near the incinerator. Sometimes we've tested it late at night, but only when asked to by state and county officials."

He said the 1,800-degree incinerator operates from 7 a.m. to 3:30 p.m., with a capability of burning 760 pounds of trash per hour, including infectious waste.

The last waste of the day is thrown in at 3:30 and must burn for at least two hours. Then the unit must cool down another two hours, all the while making its high-pitched noise.

Robert C. Merrey Jr., an official with the county's environmental protection department, said local regulations limit the incinerator a noise level of 65 decibels from 7 a.m. to 10 p.m., and 55 decibels other hours.

Mr. Merrey said he had received complaints about the incinerator noise, but the one time his office went to test the decibel level, the unit was shut down, he said.

Even if a noise violation were discovered, nothing could be done about it because the state stopped funding the enforcement of such violations in November, Mr. Merrey said.

Mr. Kennedy said the hospital has conducted its own tests of the decibel level. Its highest reading was 72, but after some modifications, the average reading was lowered to about 60, just within legal limits.

Mr. Kennedy said the hospital was taking measures to bring the level down to 55.

"We're still in the testing phase, so we're trying to work out the kinks," he said.

The state has given the hospital a temporary permit to run the incinerator.

A permanent permit will be issued if the unit passes an emissions test that was completed last month. The results of that test are not yet available.